68-I 二叉搜索数最近公共祖先

package JianZhioffer;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Queue;
/**
 * 二叉搜索树的最近公共祖先
 * 给定一个二叉搜索树, 找到该树中两个指定节点的最近公共祖先。
 */
public class test68I {
    public static void main(String[] args) {
        TreeNode t=new TreeNode(6);
        t.left=new TreeNode(2);
        t.right=new TreeNode(8);
        t.left.left=new TreeNode(0);
        t.left.right=new TreeNode(4);
        t.right.left=new TreeNode(7);
        t.right.right=new TreeNode(9);
        t.left.right.left=new TreeNode(3);
        t.left.right.right=new TreeNode(5);
        TreeNode p=t.left;
        TreeNode q=t.left.right;
        TreeNode result=lowestCommonAncestor(t,p,q);
        int x=0;
    }

    //思路：递归/迭代，p和q和最近公共祖先的关系：
    //1.都在左子树 p.val<root.val ,q.val<root.val, 那么去root.left继续判断
    //2.都在右子树 p.val>root.val ,q.val>root.val, 那么去root.right继续判断
    //3.一左一右   直接返回
    public static TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        while(root!=null){
            if(p.val<root.val&&q.val<root.val){
                root=root.left;
            }else if(p.val>root.val&&q.val>root.val){
                root=root.right;
            }else{
                break;
            }
        }
        return root;
    }
    //超出内存限制了。。
    public static TreeNode lowestCommonAncestor1(TreeNode root, TreeNode p, TreeNode q) {
        if(root==null){
            return null;
        }
        Queue<TreeNode> que=new LinkedList<>();
        List<TreeNode> ts=new ArrayList<>();
        que.offer(root);
        while(!que.isEmpty()){
            int x=que.size();
            TreeNode t=que.poll();
            for(int i=0;i<x;i++){
            if(t.left!=null){
                que.offer(t.left);
            }
            if(t.right!=null){
                que.offer(t.right);
            }
            ts.add(t);
        }
            
        }
        Map<TreeNode,List<Integer>> map=new LinkedHashMap<>();
        for(int i=0;i<ts.size();i++){
            TreeNode temp=ts.get(i);
            List<Integer> list=new ArrayList();
            helper(temp, list);
            map.put(temp, new ArrayList<>(list));
        }
        TreeNode x=null;
        for(TreeNode t:map.keySet()){
            List<Integer> list=map.get(t);
            if(list.contains(p.val)&&list.contains(q.val)){
                x=t;
            }
        }
        return x;
    }
    public static void helper(TreeNode root, List<Integer> list) {
        while(root!=null&&!list.contains(root.val)){
            list.add(root.val);
            helper(root.left, list);
            helper(root.right, list);
        }
        
        
    }
    
}